The subject matter disclosed herein relates to environmental control systems and, in particular, to environmental control systems in an aircraft.
Aircraft have power systems that are comprised of several components, such as an engine, an environmental control system and a thermal management system. These systems are designed relatively independently from each other with power being transferred from one system to another.
The environmental control system (ECS) supplies pressurized air to the cabin and flight deck of an aircraft for both comfort and pressurization. The air is drawn from either or both the compressor stage of the engine (a bleed air system) or directly from exterior air (ram air system). In more detail, bleed air is extracted from the engine core at a pre-defined stage location in the engine compressor region. Frequently, this bleed air is delivered to the aircraft at temperature and pressure states well above what can be safely accommodated by the materials of systems used to distribute the air. Thus, a typical ECS includes preconditioning devices such as heat exchangers and pressure regulating valves to adjust the temperature and pressure of the bleed air to meet distribution system requirements. This pre-conditioning of the bleed air for the distribution system wastes the energy provided by the engine in compressing the air for extraction at the bleed port. This waste of energy is manifested in increased fuel burn required to maintain the desired thrust while also providing the bleed air stream for ECS requirements. A more efficient method of utilizing more of the existing bleed air energy would result in a more efficient aircraft. While improving the energy efficiency of aircraft power systems has been attempted by employing a “more-electric” approach to engine energy extraction, these methods also have their drawbacks in terms of additional weight, cost and complexity.